Co2 sensor

[Hillside2016]

Hi recently bought a mr2 roadster which had developed a co2 sensor problem had them replaced and problem has returned . Every time I remove the code it reoccurs when it reaches normal running temperature. Also had maf sensor replaced,can anyone help
Thanks

[kambites]

Do you mean the Lambda (O2) sensor? There isn't a CO2 sensor.

[WaferThinHam]

Exactly which code are are you getting? If I remember rightly there are two lambda sensors on the 2002> MR2, but I could be wrong (mine killed a lambda a few years back).

[0ddball]

Did you use quality sensors? Or £20 ones?

[TooMany2cvs]

WaferThinHam said:

Exactly which code are are you getting? If I remember rightly there are two lambda sensors on the 2002> MR2, but I could be wrong (mine killed a lambda a few years back).

Pre- and post-cat? If the post-cat is flagging a fault, then the cat's probably dead.

[M_A_S]

TooMany2cvs said:

WaferThinHam said:

Exactly which code are are you getting? If I remember rightly there are two lambda sensors on the 2002> MR2, but I could be wrong (mine killed a lambda a few years back).

Pre- and post-cat? If the post-cat is flagging a fault, then the cat's probably dead.

Well quite. Because a sensor is registering a fault it doesn't mean the sensor is at fault.

[Hillside2016]

Thank you for your replies
The code is P O 141 o2 sensor heater circuit ,bank 1 sensor 1. I’m using a laser 5091 decoder

[TooMany2cvs]

Hillside2016 said:

Thank you for your replies
The code is P O 141 o2 sensor heater circuit ,bank 1 sensor 1. I’m using a laser 5091 decoder

So the sensor's fine, it's the heater circuit. Did you fit the right sensor? 3 or 4-wire? All the connections good and clean? No damage to the wiring? +12v coming through on the heater pin?

[Dr Doofenshmirtz]

It's a VERY common problem with the MK3s...

Looking into the engine bay you will see two sensors:
The left one is Bank 2 sensor 1 - pre-cat
The right one Bank 1 sensor 1 - pre-cat (your culprit)
If you look UNDER the rear left hand bumper you will see a third sensor: Bank 1 sensor 2 - post cat

The common 'fix' is to simply cut the 2 black wires off the sensor and fit a 15 ohm 15 watt resistor between the two black wires.
The 02 sensors are very sensitive on Toyota's and a cheapo jobbie from eBay will not work.

Welcome to the club by the way
While you've got the sensor out, shine a torch in there and make sure the pre-cat had been gutted. If you can still see a catalyst honeycomb you need to get it out ASAP. These can break down, get sucked into the engine and destroy it. The pre-cats aren't needed and the car will pass emissions no problem without it.

Edited by Dr Doofenshmirtz on Tuesday 18th September 16:19

[Hillside2016]

A big thank you for all your advice with regards to my post cat censor all be sorted and Lola that's her name has passed her mot today with no advisorys yippy

[Brads67]

Your car has a name ?

[Hillside2016]

Yes she has a name Lola might be old but she's my pride and joy